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Are All Aircraft "exactly" The Same Size?  
User currently offlineVC10er From United States of America, joined Feb 2007, 2968 posts, RR: 13
Posted (3 years 7 months 2 weeks 1 day 1 hour ago) and read 4749 times:
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Is every 747, A320, 777, A380, 737 exactly the same size and wing span, or is there an acceptable variance for every manufactured airplane? I know a plane in different extreme temps can change quite a bit. Someone from my company who worked on the LANDOR livery for Concorde said the Concorde can stretch almost a foot longer when very hot at Mach 2+ at 50,000 feet.
But on the ground can 2 747-400's come off the line with an inch different than the other in it's length or wingspan and be ok? Is there an acceptable tolerance for some variance?


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18 replies: All unread, jump to last
 
User currently offlinekanban From United States of America, joined Jan 2008, 3727 posts, RR: 27
Reply 1, posted (3 years 7 months 2 weeks 1 day 1 hour ago) and read 4607 times:
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there are differences because all the components have + - tolerances.. and the accumulation of tolerances can add inches .. likewise if they were all minus you'd have a shorter fuselage, wing, etc.. fortunately the law of averages kicks in and nothing gets distorted too far.

User currently offlineADent From United States of America, joined Dec 2006, 1395 posts, RR: 2
Reply 2, posted (3 years 7 months 2 weeks 23 hours ago) and read 4427 times:

No two items are EXACTLY the same.

There is some variation - I do not know the limits. Modern production processes tend to make a more consistent product.

Remember the proud press releases from some of the first all digital products(777, F35, etc) were assembled - and how they fit so well? It implies that was unusual in the past.

If you want some variation go back to the WW II planes put together by the thousands in a hurry.


User currently offlinenighthawk From UK - Scotland, joined Sep 2001, 5178 posts, RR: 33
Reply 3, posted (3 years 7 months 2 weeks 22 hours ago) and read 4126 times:

Quoting ADent (Reply 2):
Remember the proud press releases from some of the first all digital products(777, F35, etc) were assembled - and how they fit so well? It implies that was unusual in the past.

It sure was the case in the past, as the UK discovered when it tried to re-wing the Nimrod. They took a sample Nimrod and took the measurements needed for the wings. The wings were produced using modern techniques, and therefore had variances of just a few mm. When they came to fit those wings to the fuselages, they discovered no two fuselages were the same, and none of the wings would fit! This was due to much greater variances in the fuselage, as it was hand built.



That'll teach you
User currently offlinekalvado From United States of America, joined Feb 2006, 492 posts, RR: 0
Reply 4, posted (3 years 7 months 2 weeks 21 hours ago) and read 4041 times:

Just to be picky: even exact same aircraft would not be exact same size at different conditions: due to thermal expansion dimensions can change quite a bit. At Al expansion coefficient of 24e-6/degC, difference between same plane soaked overnight in ANC winter compared to sitting in DUB in summer can be a few inches - way more than any manufacturing tolerance
And you may want to think about Concorde - at supersonic speed airframe really heated up. 25 cm - or about 10" of a stretch..


User currently offlineVC10er From United States of America, joined Feb 2007, 2968 posts, RR: 13
Reply 5, posted (3 years 7 months 2 weeks 20 hours ago) and read 3920 times:
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Interesting because I knew it had to be so- nothing is "perfect" probably to the dismay of some! So this leads me to my final question: since a "plate" or "panel" (my words) that are rivited together to make a fuselage will expand or contract due to temperate changes will do so in all 4 directions... How do the airplane manufacturers prevent buckling?


The world is missing love, let's use our flights to spread it!
User currently offlinebj87 From Netherlands, joined Jun 2009, 448 posts, RR: 0
Reply 6, posted (3 years 7 months 2 weeks 18 hours ago) and read 3869 times:

A couple of weeks ago I read an article in a magazine about this subject.

Now, I don't know if the following story is 100% true but it is relevant to the subject.

KLM used to fly a bunch of DC8-63 aircraft and they noticed that one of the aircraft actually burned a lot more fuel on a given mission than the other aircraft in the fleet. The situation was so bad that they could not use the aircraft on certain routes. The plane was supposedly also a pain to fly.

In the end they decided to check out the entire plane and also did a measurement of the fuselage. It turned out the plane was everything but straight. It was actually quite a lot shorter on one side than the other which explained the extra fuel burn and odd handling.

A couple of years later when Suriname Airlines began operations KLM donated a DC8, care to guess which one?


View Large View Medium
Click here for bigger photo!

Photo © Udo K. Haafke



Anyway, don't know if this is true or just a great story.

(edit: word order)

[Edited 2011-04-13 04:51:50]

[Edited 2011-04-13 05:39:07]

User currently offlineNorthwest727 From United States of America, joined Jul 2005, 491 posts, RR: 0
Reply 7, posted (3 years 7 months 2 weeks 15 hours ago) and read 3751 times:

With more computerized controls and "robotic" equipment manufacturing airplanes, I'd say that the differences between aircraft have shrunk considerably, but that doesn't eliminate them. I can't say anything about size, but with weight, yes. With the 777, for example, at least when it was first manufactured, the sealant on the wing spars (which form part of the fuel tanks) hand to be applied by hand, using a spray gun. Obviously, lots of room for variance there, which would make the airplanes weight much differently.

User currently offlineUAL747 From , joined Dec 1969, posts, RR:
Reply 8, posted (3 years 7 months 2 weeks 12 hours ago) and read 3596 times:

A 747's wingspan varies, as do most large span aircraft, depending on how much fuel it is carrying. I believe the wingspan increases about a foot with heavier fuel loads.

User currently offlinefr8mech From United States of America, joined Sep 2005, 5599 posts, RR: 15
Reply 9, posted (3 years 7 months 2 weeks 6 hours ago) and read 3460 times:

Quoting VC10er (Thread starter):
or is there an acceptable variance for every manufactured airplane?

This is why many structural components, primary and secondary, and exterior panels come from the manufacturer undrilled. When we have to relace one of these parts, they are fit into place (where possible) and then drilled or we pick-up the holes from the old part and drill.



When seconds count...the police are minutes away.
User currently offlinekanban From United States of America, joined Jan 2008, 3727 posts, RR: 27
Reply 10, posted (3 years 7 months 2 weeks 1 hour ago) and read 3358 times:
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Quoting UAL747 (Reply 8):
A 747's wingspan varies, as do most large span aircraft, depending on how much fuel it is carrying. I believe the wingspan increases about a foot with heavier fuel loads.


I would question that only because the upper and lower skins plus the front and rear spars can not grow and shrink.. they are one piece .. now if they "grow" because the curvature changes , that's another story


User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 11, posted (3 years 7 months 2 weeks ago) and read 3335 times:

Quoting kanban (Reply 10):
I would question that only because the upper and lower skins plus the front and rear spars can not grow and shrink.. they are one piece .. now if they "grow" because the curvature changes , that's another story

Dihedral...as you increase fuel load the wing flexes down and, since it was slightly bent up to start with, the span gets larger.

Tom.


User currently offlinejwenting From Netherlands, joined Apr 2001, 10213 posts, RR: 19
Reply 12, posted (3 years 7 months 1 week 6 days 21 hours ago) and read 3293 times:

Quoting bj87 (Reply 6):
Anyway, don't know if this is true or just a great story.

I'd guess that if it were that bad it wouldn't have passed QA testing and pre-delivery customer testing.



I wish I were flying
User currently offlineoly720man From United Kingdom, joined May 2004, 6839 posts, RR: 11
Reply 13, posted (3 years 7 months 1 week 6 days 17 hours ago) and read 3245 times:

Quoting bj87 (Reply 6):
A couple of weeks ago I read an article in a magazine about this subject.

Wasn't the April 1st edition was it?



wheat and dairy can screw up your brain
User currently offlinekanban From United States of America, joined Jan 2008, 3727 posts, RR: 27
Reply 14, posted (3 years 7 months 1 week 6 days 15 hours ago) and read 3186 times:
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Quoting tdscanuck (Reply 11):
Dihedral...as you increase fuel load the wing flexes down and, since it was slightly bent up to start with, the span gets larger.

that's the word I was looking for.. however that span increase is only temporary... I think the original question was more about differences betweeen actual planes.. and that goes back to the accumulation of tolerances (which we used to say always happens at the worst possible spot.)


User currently offlineGBLKD From United Kingdom, joined Jan 2011, 345 posts, RR: 0
Reply 15, posted (3 years 7 months 1 week 6 days 13 hours ago) and read 3136 times:

Quoting nighthawk (Reply 3):
It sure was the case in the past, as the UK discovered when it tried to re-wing the Nimrod. They took a sample Nimrod and took the measurements needed for the wings. The wings were produced using modern techniques, and therefore had variances of just a few mm. When they came to fit those wings to the fuselages, they discovered no two fuselages were the same, and none of the wings would fit! This was due to much greater variances in the fuselage, as it was hand built.

A similar problem happened when modifying Concorde post AF4590 apparently. It was the kevlar fuel tank liners that caused a bit of head scratching as no two aeroplanes were quite the same size.


User currently offlinebj87 From Netherlands, joined Jun 2009, 448 posts, RR: 0
Reply 16, posted (3 years 7 months 1 week 6 days 12 hours ago) and read 3100 times:

Quoting oly720man (Reply 13):
Wasn't the April 1st edition was it?

You actually got met to go: uhhh, o god....... and get up and check. Thank goodness the answer is no, man would have been a stupid mistake.   

The article was published in the February issue of the Dutch aviation magazine Piloot en Vliegtuig, page 65. It was written by a journalist called Wim Kroese, gotta give credit where it is due, so if the story is fake it is on him.

[Edited 2011-04-14 10:55:50]

User currently offlineBlueJuice From United States of America, joined Jun 2010, 250 posts, RR: 0
Reply 17, posted (3 years 7 months 1 week 6 days 11 hours ago) and read 3095 times:

On another aviation forums, one person told the story of a DC-9 from his time working as a machinist at McD. Whether the story is true or not is still a mystery to me. Still a nice one though along the same lines as the DC-8 tale. The story goes that a DC-9 for carrier he declined to name was in a jig when a earthquake hit. Ended up torquing the airframe pretty badly but still within spec. The plane was completed and pushed out the assembly line. From that time on, the place needed lots of trim to keep to flying straight. According to the poster, the plane has since been scrapped and no longer graces the skies. Even if untrue, still makes a good story.

User currently offlinekanban From United States of America, joined Jan 2008, 3727 posts, RR: 27
Reply 18, posted (3 years 7 months 1 week 6 days 10 hours ago) and read 3046 times:
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I wonder if the AF pilot will use differing wing spans between the A380's as the reason for the NY encroachment?   

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